Kites



R. P. HOLLAND, JR

Aug. 15, 1967 KITES 3 Sheets-Sheet 1 Filed April '1, 1965 g- 15, 1967 R.P. HOLLAND, JR 3,335,984

KITES Filed April 1, 1965 3 Sheets-Sheet 2 g- 15, 1957 R. P. HOLLAND, JR3,335,94

KITES Filed April 1, 1965 3 Sheets-Sheet 5 United States Patent3,335,984 KITES Raymond Prunty Holland, Jr., 1702 W. 3rd St.,

Roswell, N. Mex. 88201 Filed Apr. 1, 1965, Ser. No. 444,550 14 Claims.'(Cl. 244-153) This invention relates to kites and particularly toaerodynamically balanced kites of the types described in US. Patents2,562,789 and 2,698,724. The improved kites will be of simplerconstruction, without a bridle and without a trailing tail, and may beflown in stable flight or in aerobatic flight, at the choice of the kiteflier, in a wide range of wind conditions.

In a kite intended for popular use as a toy or for sport the desirablecharacteristics are: simplicity; light weight; durability; economicalconstruction and packaging; ease and infallibility of assembly by theuser; ease of launching; certainty of satisfactory flight, whether thewind is light or strong, or whether it is steady or gusty; aerodynamicstability in flight without the use of a rag tail or other auxiliarydevice; rigidity of form in flight; resiliency of structural members toreduce accidental breakage; eflicient aerodynamic form resulting in highflights or aerobatic flights at the choice of the kite flier; lightstring pull enabling thin string to be used, reducing string drag andpermitting high flights to be performed; ability to fly very high withseveral kites on one string; striking appearance, preferably like aplane or a bird; and unique flying abilities which set it apartdistinctly from all other kites.

Heretofore no kite has accomplished all of these desirable features inone construction.

The object of this invention is to provide all the desirable featureslisted above in one novel structure.

It is a further object of this invention to provide novel means offlight stabilization for kites, and means for their adjustment.

This invention in its preferred form employs a novel structure whichuses a border string around the tips of two crossed sticks, one of whichextends forward well clear of the lifting surface, both sticks beingbent concave upwardly, the wing stick also being bent concaverearwardly, these sticks supporting wing and tail cover material concaveupwardly both laterally and directionally, and having unique upwardlyforwardly sloping, rearwardly outwardly skewed jib-like stabilizersurfaces at the wing tips. These stabilizers and the tail surfacecontribute to a striking bird-like appearance, which is most pronouncedin flight when wind pressure is on the wing cover material.

The construction of the kite will be seen from the drawings, which showthe preferred embodiment of the invention and several alternate for-ms.

FIGURE 1 is a top plan view of the preferred embodiment of the inventionhaving the flight appearance of a hawk. FIGURE 2 is a sectional sideview along line 2-2 of FIGURE 1 showing the cross section and allportions of the kite lying beyond the cross section. The front of thekite is at the top in FIGURE 1 and at the left in FIGURE 2. In itsflight attitude the front end of the kite is relatively higher than isshown in FIGURE 2. The upwardly concave form of the kite, bothlongitudinally and laterally, is to be seen in FIGURE 2. FIGURES 3 and 4are enlarged sections of the wing tip of the kite taken at 3-3 and 4-4respectively of FIGURE 1, show- 'ice ing the form of the jib-likestabilizer surfaces. These produce locally increased upward concavity ofform at the wing tips, both longitudinally and laterally. The sectionthrough wing stick 2 in FIGURE 4 appears broad because line 4-4 cutsthrough the stick at a small angle. FIG- URE 5 is an enlarged sectionthrough the leading edge of the wing root at 5-5 of FIGURE 1. Thecurvature of the sheet material in FIGURES 3, 4, and 5 is due to thewind pressure; the forms shown are those which exist in flight.

FIGURE 6 is a diagram representing the kite as seen from the rear andsomewhat above showing how wing warping is accomplished for trimming theflight position of the kite laterally, by sliding the front of the nosestick sidewardly on the front border string loop.

FIGURE 7 shows the rig adjuster used for shortening and lengthening thefront border string loop to obtain the configurations shown in FIGURES8, 9, and 10.

FIGURES 8, 9, and 10 are front views of the kite taken in a directionparallel to the local air flow over the wing, showing the effect ofshortening and lengthening the front border string loop on theaerodynamic frontal aspect of the kite, for the purpose of varying thedrag and the stability of the kite.

FIGURE 11 is a view along the direction of the relative wind across thewing when the kite is yawed, showing the effect of the wing tipstabilizer surfaces on the frontal aspect of the yawed kite. Thesestabilizer surfaces have the purpose of imparting directional stabilityto the kite.

In FIGURES 8 through 11 the amount of frontal bow in the wing stick isexaggerated to show more clearly the differences caused by rigging.Horizontal tail 11 is omitted from FIGURES 9-11 for clarity.

FIGURES 12-19 show four alternate embodiments of the invention. Evennumbered figures show plan views and odd numbered figures show sideviews. Each plan view shows a fore and aft dashed line on the rightwing, and each side view shows the shape of this line in side view, toillustrate the form of the jib-like wing tip stabilizers.

FIGURES 12-17 show all-wing versions of the invention. In FIGURES 12-13a rearwardly bowed wing stick is used. In FIGURES 14-15 two sweptbacklateral spars anchored rigidly in a central socket member replace thebowed wing stick, producing a kite having the appearance of a supersonicairplane. In FIGURES 16-17 the forward loop of the border string hasbeen eliminated, its formpreserving function being performed by rigidleading edge sticks secured rigidly in a central socket member integralwith a rigid forwardly extending member the function of which is to movethe center of gravity of the kite forward. It will be observed that theleading edge member is elevated higher than is the lateral member lyingbehind it, so that the angle of attack of the jib-like stabilizersurface is greater than is the angle of attack of the remainder of thelifting surface. This is true of all forms of the invention. Theconstructions in FIGURES 14-17 are adaptable to demountable structurewith short sticks which can be packed in a short package. It will beobserved that the central body member in these kites is held concaveupwardly by the tension of the wing cover material and of the borderstring. This concavity is somewhat exaggerated in the figures in orderto be plainly visible.

FIGURES 18-19 show an embodiment of the invention in the form of anairplane without a vertical tail but with wing tips upturned and skewed,performing as directional stabilizers in accordance with the teaching ofthis invention. This version of the invention would be fabricated usinga rigid foamed plastic material molded in a single piece. The forwardlyextending fuselage member has the function of moving the center ofgravity forward.

In US. Patent 2,562,789 the trim and stability of kites was improved bythe use of a forwardly extending member moving the center of gravity ofthe kite forward, bringing the center of pressure, the center ofgravity, and the point of action of the pull of the flying string closerto each other than previously, so that any changes in the major forcesacting on the kite would produce smaller distributing moments on thekite than previously. In US. Patent 2,698,724 these benefits wereretained and in addition the kite was provided with longitudinalconcavity in an upward direction, so that the ballasted trailing tailand the flying string bridle of the previous patent were no longerneeded. At the same time a simpler, lighter structure was accomplished.

In the present invention this trend of improvement is continued. Meansof providin directional stability have been invented which requireneither a trailing tail nor a vertical tail. In addition means wereinvented for adaptability to light, strong, steady, or gusty winds, andfor enabling the kite flier to select steady flight or aerobatics, orhigh angle free-wandering soaring flights or low angle flights with aminimum of lateral movement. This has all been accomplished in astructure simpler and lighter than that of the aerodynamically balancedkites referred to by patent number above. The result is a tailless,bridleless, kite structure of marked simplicity and lightness, havingunique stability and versatility.

The results achieved by the present invention are produced byconstructional features which combine and interact with each other in amost critical and delicate manner, and yet when they are combined astaught in this invention the results are insensitive, such that evensmall children can fly the kite with reliability and satisfaction.

The use of jib-like stabilizers at the Wing tips for producingdirectional stability and increasing lateral stability, would producedirectional instability rather than directional stability if there werenot a forward-extending exposed body stick at the front of the kite tocause the center of gravity of the kite to be well forward. The forwardend of the body stick, in turn, provides a simple light weight supportfor the jib-like stabilizers, properly positioned by virtue of theupward bend of the body stick to give the stabilizers their requiredupward tilt. The combined result exceeds the individual contributions ofthe components; the elimination of either the bare nose stick or thejib-like stabilizer would result in an unstable kite and an incompletesupporting structure.

The combined directional stability effect of the jiblike stabilizers andthe forward center of gravity is like that of a snow plow pulled from aforward point. In the kite, stability must be achieved in gusty air,when the kite is battered by side gusts. In these conditions the pointwhich is equivalent to the towing point of the snow plow is the centerof gravity of the kite. A rearward center of gravity on the kite is likea rearward towing point on the snow plow. It is obvious that a snow plowtowed forward by a rope attached to the rear of the plow would beunstable, but that when it is towed from a more forward point it becomesstable. The same is true of kites having V-forms. Although they may bestable in steady air when flown from a string tie point forward of thecenter of gravity, they are unstable in gusty air when the dynamicinertia reaction acts at a rearwardly located center of gravity, and notat the string tie point. Then a side gust turns the kite further to theside, like a weathervane facing backward.

Although this invention employs a sort of snowplow stability, it neednot resemble the snow plow in appearance. This is because the center ofgravity of the kite is relatively well forward, due to the forwardlyextending body stick. Consequently, the kite may employ wings at rightangles to the direction of flight, and may accurately simulate theappearance of birds or of subsonic airplanes. Such appearance is avaluable feature in kites to be sold as toys.

There have been relatively few kite constructions which produce a steadykite position in choppy winds. Most steady kite forms depend on eithersome kind of trailing tail or upon large aerodynamic drag. But thetrailing tail is an inconvenience and high drag prevents aeorbaticflights which are desirable for sport. The present invention solves bothof these problems.

It has long been believed that a kite without a trailing tail requires abridle. The present invention shows that this is not true; it istailless and uses no bridle. This has practical advantages for the sportof kite flying; the present invention permits a kite to take ofi fromthe ground like a plane, unencumbered either by a bridle beneath or atail behind. As a result it can take off and land by itself as the windrises and falls. It is always in trim in pitch, whether at the groundlevel or at its greatest angle of elevation. This is not true of anykite which uses a bridle or the equivalent of a bridle, such as a keel,or any other rigidly held flying string tie point well below the liftingsurface of the kite, by whatever name called.

The present invention adds to the kite art means for attainment ofdirectional and lateral stability in the proper relative proportions,means for adjusting the stability and for adjusting the drag, and meansfor trimming the kite so that it will fly directly downwind, or eitherto the right or to the left at the kite fliers option. These benefitsare accomplished without any significant increase in weight orstructural complexity.

Directional stability in aircraft is conventionally accomplished byvertical tail surfaces. In an aerodynamically balanced kite any weightadded at the rear of the kite due to vertical tail surfaces requires atleast as much weight to be added at the front of the kite to restorebalance. As a result of this and because of the practical diflicultiesencountered in designing a simple kite embodying vertical tail surfaces,such surfaces are very seldom used successfully, and are never usedefficiently. In the present invention the simple jib-like stabilizers onthe wing tips accomplish directional stability and contribute to lateralstability, without affecting the balance or the weight of the kite.

An aerodynamically clean kite has an inherent tendency toward activemotions in gusty air, being able to draw suflicient energy from the windto perform large lateral movements. These movements generate additionalvelocity at the kite over that due to the natural wind. A sufficientlyclean kite which responds to gusts, flying in sufliciently gusty airmust unavoidably becomes disoriented. This is because the wind speed atthe kite due to the kites own movements becomes large as compared to thenatural wind speed and the kite as a responsive mechanism has no way ofsensing the direction from which the natural wind is coming, and itsrandom flight sooner or later carries it to the ground. It is thereforedesirable to be able to increase the drag of a kite conveniently toadapt it to steady flight in gusty wind. This invention provides thatadjustment, with no significant increase of weight or complexity.

For a kite without a trailing tail to remain aloft in the fastestpossible wind it must have no avoidable movements laterally. Any kitehas a certain limited rigidity of structure. As the wind speedincreases, all the forces on the kite including the pull of the flyingstring increase as the square of the wind velocity, except the kiteweight, which remains constant. The weight is the only force whichprovides the tailless kite as a responsive mechanism with a sense of thevertical direction. At some particular high speed the unsymmetricalforces on the kite due to unsymmetrical structural deflections mustoverpower the kites ability to react correctively in response to itsvertical weight force, and flight disorientation due to speed alone mustoccur. Such disorientation occurs at a relatively slower wind speed whenthe kite has lateral movements of its own-for two reasons: (1) thelateral movement increases the true resultant airspeed at the kite, and(2) the lateral acceleration of the kite causes the mass accelerationreaction force to move away from the vertical. Consequently, lateralmovements must be reduced to a minimum if a tailless kite is to stayaloft in the strongest possible winds. This may be done in part byincreasing the drag of the kite, causing the kite to seek a downwindposition at all times. But a large drag is undesirable at slower windspeeds in that it prevents aerobatics and high angle flight. Therefore,for these additional reasons, the drag of a kite should be adjustable,as it is in this invention.

The kite of the present invention is able to fly in very light breezes,because of its light weight structure. Its structural features alsopermit it to fly in relatively strong winds. It is a pre-stressed,pre-defiected structure, with both sticks bowed and with astretch-resistant border string in tension around its perimeter. Noimportant distortion of its supporting frame can occur until the windbows these sticks more than they are already bowed. When the kite isrigged for steady flight, both sticks are deeply bowed so that acorrespondingly very strong wind is needed to bend them further. Inaddition the rearward bend of the wing stick places that member .partlyon edge so far as air loads are concerned, increasing its mechanicalstiffness against air loads.

These aspects and other aspects of the invention will be seen moreexplicity by reference to the drawing. In the figures the thicknesses ofsome of the parts are greatly exaggerated in order to be visible.

In FIGURE 1 body stick crosses wing stick 2 at its midpoint where thesticks are bound together by cord 3. Border string loop 4 engages in thetips of sticks 1 and 2, in thin slots not shown, and holds the sticksbent in an upwardly concave form, with wing stick 2 also bent concaverearwardly. Wing lifting surface 5 is a thin film material, attached toborder string 4 by means of adhesive tape 6. Flying string 7 is tiedaround stick 1 at a single point, passing through eyelet 8, slightlyforward of the center of gravity of the kite. The center of gravity iscloser to the leading edge of surface 5' than it is to its trailing edge9. Flying string 10 ties through eyelet 8 from above the kite andextends to another kite flying higher. Horizontal tail surface 11, ofthin film material, is attached to border string loop 4 by tape 6, in aconstruction similar to that at the wing tips. Wing surface 5 and tailsurface 11 are attached to body stick 1 by adhesive tape not shown. Wingtip flags 12 are attached to border string loop 4 outboard of the tipsof wing surface 5 and rearward of the tips of wing stick 2; they areheld in place by adhesive tape not shown. Flag 12 is a folded card whichserves as an identification or instwction label and also occupies therearward portion of the exposed border string beyond the tips of wingsurface 5 to prevent the assembly of wing stick 2 to border string 4 inthat region. In this way flags 12 assure symmetrical assembly of thekite. Rig adjuster 13 is attached in border string loop 4 between thenose end of body stick 1 and the tip of wing surface 5. Rig adjuster 13is indicated here diagrammatically by a rectangle. Its construction isshown in FIGURE 7. Tapes 14 wrap around tapes 6 and the wing filmmaterial, above and below, at the ends of adhesive tape 6 at the forwardouter tips of wing surface 5.

Leading edge 15 of lifting surface 5 extends from body stick 1 to borderstring loop 4. At one point on each side of the kite a tuck is taken inleading edge 15 to remove slack. This tuck is covered and held in placeby adhesive tape 16.

The function of the thin upturned leading edge 15 is twofold: (1) Itserves to produce a local airflow separation along the leading edge ofthe wing causing the areodynamic center of pressure of the wing to moverearward. This is just as effective for stability in pitch as moving thecenter of gravity of the kite forward by the same amount, and isaccomplished more easily and without the increase of weight which wouldbe required otherwise. (2) Being elastic and held in tension by theoutward thrust of bent wing stick 2 and by the forwardly spreadingaction of tension in string loop 4, edge 15 take a relatively flat lowdrag position in a light breeze, as shown in FIGURE 5 in solid lines,and blows up to a more steeply inclined high drag position in strongerwinds, as shown by dotted lines in FIGURE 5. This action automaticallyincreases the drag of the kite to some extent when greater drag isneeded for increased stability.

The portion of the leading edge of wing surface 5 which is outboard ofedge 15 is supported by border string loop 4. This edge is also upturnedso that it also serves to produce a local airflow separation asdescribed above.

Jib-like stabilizer surface 17 is the region of wing surface 5 forwardof stick 2 and outboard of tape 16. FIGURES 3 and 4 show sections ofstabilizer 17. FIG- URE 3 shows the forward-upward general slope of itssurface in a vertical fore and aft cross section. The general slope ofthe surface of stabilizer 17 is that of a forwardly-upwardly tiltedoutwardly-rearwardly skewed rim on the forward outward tip of wingsurface 17.

In FIGURE 4 the section through wing stick 2 is at an angle, producingthe large section shown. In FIG- URES 3, 4, and 5 the thicknesses of 4,5, 6, 14, and 15 are enormously exaggerated, as required to showthicknesses.

Tail surface 11 as shown in FIGURE 1 contributes to the bird-likeappearance of the kite, and performs the function of horizontalstabilizer. With this construction there need be no rag tail or trailingtail of any kind to detract from the kites appearance or to causeinconvenience, or to be lengthened or shortened as wind conditionschange, and there is less Weight to be supported and less drag to beencountered than would be the case if a trailing tail were used.

Tail surface 11 is supported at its outer rear edges by being taped toborder string 4. The rear portion of border string 4, being that portionrearward of wing stick 2, is held in tension at all times, regardless ofthe adjustment of the front portion of the border string, by therearwardly concave bend of wing stick 2. The tension in the rear loop ofborder string 4 holds the rear portion of body stick 1 bent concaveupwardly, thereby setting tail surface 11 at a smaller angle of attackthan that of wing surface 5, as is necessary to hold the nose of thekite high in flight. This feature is essential in a bridleless kitehaving a forward center of gravity.

The rearwardly concave bend in wing stick 2 also produces the requiredform for stabilizer surfaces 17, which in turn produces many benefits,to be described in detail below. As seen in FIGURE 1 the rearward slopeof wing stick 2 near its outer ends determines the slope of the rearwardedge of stabilizer surface 17. Also, as may be seen in FIGURES 2, 3, and5, the cross section of wing stick 2 is a rectangle having a shorterdepth in the plane of the bend of the stick than it has in a directiontransverse to the plane of the bend. When the stick is bent rearward thestick is stiffened so far as air loads are concerned. Its cross sectionis rotated to produce a greater effective beam depth to resist the majorwing bending loads. These loads act in a direction normal to the surfaceof wing 5.

The use of adhesive tape to attach border string 4 to lifting surface 5and tail surfacell, by applying the tape to only one side of the surfaceand by creasing it down along both sides of the string to adhere closelyaround the string, as shown in FIGURES 1, 3, and 4, solves severalproblems of long standing in the manufacture of kites employing thinplastic film supported at the edges by string. Suitable plastic filmsfor such kites are mylar and polyethylene, both of which have beendifficult to attach in the past. For example, the attachment of stringto polyethylene using liquid adhesives is unsatisfactory. The adhesivesare not reliable and they often run out of place and spoil the productby discoloration and by sticking the wrong parts together. Heat sealingdistorts the film and does not hold the string. Various sorts of coatedstrings and strings having fibers projecting from them for the purposeof being held between two heat sealed or glued surfaces have been tried.Strings have been held by the use of double coated pressure sensitivetape folded around the string, and with the plastic film fold around theoutside, where it was either taped or glued down. This was expensive inmaterials and labor, requiring the kite assembler to work on both sidesof the film, and it did not hold satisfactorily.

These problems were solved by the very simple construction taught inthis application. The resulting joint is superior for thin-filmstring-rigged kites because the load is distributed from the string intothe film. There is no rigid mechanical restraint holding the string atany one point, except at terminal reinforcing tapes 14, the function ofwhich is to keep border string 4 from coming out completely from betweenthe film surface and tape 6. The construction permits border string 4 toslip sidewardly somewhat at points of maximum stress until an adjacentportion of the string (and of the film to which it is attached) carriesas much stress. The border string takes the form of a catenary curvewhich is highly desirable for uniform distribution of stresses but whichcould not be put in by even the most elaborate tooling, even if its formcould be computed. The tapes and strings are simply assembled instraight lines, and in their first use they take permanent catenarycurves. This novel string anchoring construction permits a thinner filmto be used, saving weight and cost, and prevents distortion of the filmmaterial, improving appearance and flight performance. The string isheld at every point because of its intimate contact with the adhesive onthe tape and will not slip lengthwise, a result not previouslyaccomplished with complete reliability by any other method. Labor costsof kite assembly dropped markedly when this construction was introducedin production.

A wing warping action is accomplished in this invention by sliding thefront end of nose stick 1 sidewardly along border string 4, as indicatedby arrow A in FIGURE 6. This figure is a view of the kite as it would beseen in flight from a position downwind from the kite and somewhathigher, after the front end of the nose stick has been displaced alongthe border string to the viewers right. This hows the body sticksidewardly, moving it to the left at the trailing edge of the wing, asindicated by arrow B. Due to this movement, the trailing edge 9 of thewing is pulled taut at C and is slackened at D, points F at fourlocations being held in place by the structure described above. The wingwarping so accomplished lowers the trailing edge of the wing at C,having the effect of a lowered aileron on the right wing, and raises thetrailing edge at D, having the effect of a raised aileron on the leftwing. As a consequence the kite experiences an aerodynamic rollingmoment in the direction of arrow E, lowering the left wing and raisingthe right wing, and consequently rolling the kite to the left.

Secondary but important effects of this wing warping are as follows:Horizontal tail surface 11 is warped directionally and stabilizersurface 17 on the right wing is made to stand up higher than stabilizersurface 17 on the left wing. These actions produce a yawing moment onthe kite in a direction to move the nose of the kite to the right.

The combined action of the primary and secondary effects described aboveis that of applying crossed controls to the kite, as used in an airplaneto make its sideslip rather than to make it turn. The secondary actionconverts the roll of the primary action into a sideslip and the kitesimply moves over to the observers left into a new stabilized position.

Rig adjuster 13 in FIGURE 7 consists of plate 18 in which are mountedthree eyelets 19. One end of string 4 is tied into a terminal loop 20.The other end of string 4 is threaded in and out through eyelets 19,through loop 20, and back through eyelets 19, each in the oppositedirection this time, and through head 21. The end of string 4 is knottedso it cannot slip back through head 21, and bead 21 is too large to passthrough eyelet 19. String loop 4 is shortened by pulling head 21 awayfrom loop 20, and is lengthened by the opposite movement. Plate 18, whenplaced in the position shown in FIGURE 7, crimps string 4 and preventsslippage. To permit slippage for adjustment, string 4 is slackenedlocally at plate 18.

The effects of using rig adjuster 13 are illustrated in FIGURES 8, 9,and 10, which depict the frontal aspect of the kite as it presentsitself to the local wind direction at the wing. In FIGURES 8 and 9 (andin FIGURE 2 above and FIGURE 11 below) the amount of bowing preferablyemployed in the kite is somewhat exaggerated for clarity.

FIGURE 8 shows a medium amount of bowing of the kite, with rig adjuster13 a moderate distance from the nearby stabilizer surface 17. FIGURE 9shows a larger amount of bowing, with rig adjuster 13 a greater distancefrom stabilizer 17, and with the length of border string loop 4shortened accordingly. FIGURE 10 shows a minimum amount of bowing, witha maximum length of string loop 4, and with rig adjuster 13 directlyadjacent to stabilizer 17.

A medium adjustment (FIGURE 8) is used for most flying conditions; aheavily bowed adjustment (FIGURE 9) is used for strong gusty winds; anda flat adjustment (FIGURE 10) is used for smooth winds and foraerobatics in gusty winds.

It is apparent from the figures that the aerodynamics drag of the kiteis greater as the border string loop is shortened, causing stabilizersurfaces anl leading edge 15 to rise. This produces more force to holdthe kite downwind, and absorbs energy which might otherwise impartlateral velocities to the kite.

When rigged as in FIGURE 10 the kite is clean aerodynamically; thefrontal area is small and the span is long; the kite is capable ofriding rising thermal currents until it seems to be directly overhead,with the flying string slack, and if energized by gusty air and ifcontrolled by properly timed pulls and releases of the flying string thekite can be made to perform complete loops in the air or long dives atthe earth with last-second pull-outs.

The action of stabilizers 17 in producing directional stability is dueto the rearward outward slope of these surfaces in combination with arelatively forward center of gravity, in an action which could becharacterized as snowplow drag stability. Both stabilizers produce drag.When the kite faces directly into the wind the drag on the two sides isequal. But when the right wing tip moves forward stabilizer 17 on theright side develops more drag than stabilizer 17 on the left side,because the right side faces the wind more nearly squarely and the leftside slopes away more. The role of the center of gravity is that thekite rotates around its center of gravity when sharply disturbed bygusty wind, and the position of this dynamic axis of rotation determineswhether the moment arms at which the drag forces act are favorable orunfavorable for stability. A relatively forward center of gravity causesthe effects of the moment arms to be small, even though the center ofgravity may not be sufficiently far forward to produce a stabilizingeffect from the changes of moment arms. (It would be necessary for thecenter of gravity to lie forward of a line connecting the centers ofpressure of stabilizer surfaces 17 for such a stabilizing effect toexist.)

The more sharply the stabilizer surfaces are skewed back and the morerearwardly they are located on a kite, the more rearward may the centerof gravity be, in obtaining a given degree of directional stability ingusty wind. But the difficulties arise from pitching stability when thecenter of gravity is allowed to be rearward, and of course, as describedabove, it is desirable to achieve directional stability in a kite whichhas no perceptible sweepback to the casual observer, in order that thekite may have the form of a soaring bird or a subsonic airplane. Such aform has a wing of relatively high aspect ratio. This has the furtheradvantage of having less induced drag than is possible with kites ofshort span and swept form. The achievement of small induced drag enablesthe bird-like kite to fly higher and at a steeper angle of elevation,particularly when rigged relatively flat to keep other forms ofaerodynamic drag at small values, than is possible with the highly sweptshort form of wing. The large wing span of the bird-like kite producesstill another advantage: the lateral distance between stabilizers 17 islarge, so that a relatively small distance of drag on the two oppositestabilizers produces a relatively large stabilizing moment. Consequentlystabilizer surfaces 17 may be relatively small in area, and thereforethey increase the drag of the kite only a relatively small amount toproduce the desired degree of directional stabilization. Some smallamount of drag increase is always desirable in any case to avoidexcessive sensitivity to wind turbulence.

The disclosed structure of the invention leads inherently to therequired relatively forward center of gravity. Body stick 1 extends wellforward of lifting surface 5. Open space exists between leading edge 15and the front portion of string loop 4. The forward extension of bodystick 1 is long and slender; this reduces weight for a given balancingaction as compared to a shorter broader member, and it provides afavorable forward pulling angle enabling border string loop 4 to keepstabilizer surfaces 17 well spread forwardly.

The directional stability action of jib-like stabilizer surfacesv 17 isshown in FIGURE 11, which is a drawing in true proportions of the kiterigged as in FIGURE 9 and yawed slightly. The. angle of yaw in FIGURE 11is the same as the angle of flying string 7 as shown in FIGURE 1. Itwill be seen that the forwardly displaced stabilizer surface 17, to thereaders left, in FIGURE 11, is noticeably larger in frontal area than isthe rearwardly displaced stabilizer 17 to the readers right. Thereforethe forward wing tip (to the readers left) is pushed rear-ward by airdrag more strongly than is the rearward wing tip (to the readers right).That is, a differential force exists which, if the moment arms on thetwo sides of the kite were equal, would act to restore the kite toward aposition of zero yaw. Whether or not the kite is rotated in the desiredstabilizing direction, however, depends upon the relative moment arms atwhich these tip drag forces act.

In smooth air, in response to very gradually applied forces the kiterotates around pivot axis G in FIGURE 11 which passes through the stringtie point; around this axis it may be seen that the moment arm to theouter end of the forward wing tip (at the left) is greater than themoment arm to the outer end of the rearward wing tip (at the right). Itis easily understood, then, that static directional stability existsaround axis G, under the conditions specified. In sharply gusty air thekite rotates in yaw on pivot H through the center of gravity. Now themoment arms on the two sides are changed by the amount of the separationof axes G and H, in a direction to decrease static stability. The staticdirectional stability of the kite may become marginal if the center ofgravity is not sufficiently far forward (if axis H is very much to theleft of axis G on FIGURE 11). If the kite did not employ the projectionof body stick 1 forward of leading edge 15, the center of gravity of thekite would be farther rearward and the kite would rotate in gusty airaround axis I of FIGURE 11. In this event the moment arm to the forwardwing would be shortened and the moment arm to the rearward wing would belengthened to such a degree that the kite would be unstabledirectionally in gusty air, despite the greater drag on the forward wingtip. In addition static pitching instability would exist, which,coupling with the yawing instability, would make the kite totallyunmanageable in all winds but those which are ideally smooth.

For kite stability it is necessary that the kite have lateral stability,as produced by the dihedral of the wing, and have it in an amount whichis in the proper proportion to the kites directional stability,described above. It is desirable, further, that both these stabilizingeffects be strong when needed for the purpose of achieving stability instrong gusty winds, and that they be weak for the opposite purpose ofpermitting aerobatics to be performed. Furthermore, whether strong orweak, these two forms of stability must remain in proper relativestrengths. The desired adjustment of the power of stabilization and thecorrect balance between the two forms are achieved in this invention, ina very light simple structure. When rig adjuster 13 is used to increasethe amount of bowing of the wing as seen from the front, the effectivedihedral angle of the kite is increased. At the same time and inapproximately the same proportion the tip stabilizers are caused to beraised, increasing their frontal area and increasing directionalstability. This one action achieves all the desirable effects described.

Referring again to FIGURE 11, and considering the design of a kite whichis. able to perform aerobatics, it is necessary to have only a smallmargin of static directional stability around axis H through the centerof gravity, including any contributions to directional stability fromthe tail surfaces. Then the kite will exhibit a tendency towardinstability in gusty air when rigged flat as in FIG- URE 10 but willcorrect itself during brief recurring moments when the air is steady.

In flying the kite when rigged for aerobatics, the tendency towardinstability in a gust of wind is increased by a pull on the string. Thisis especially effective when the kite already has a laterally inclinedheading. It gives the kite an impulse toward further deviation,producing greater lateral velocity, greater total airspeed at the kite,and greater structural deflection, all of which decrease stability andlead to stunts. To return to steady flight, the flying string ismomentarily allowed to run out. This lowers the relative airspeed at thekite, allows the lateral velocity to decrease, and reduces thestructural loads on the kite, all of which increase stability. The kitewill resume a normal position. right side up, headed into the naturalwind, in this invention. When this occurs, the string is held or may bedrawn in smoothly and the kite will climb normally, until the kite flierchooses to make it stunt again.

In flying the kite of this invention recovery from stunting maneuverswill often occur naturally because, in descending, the kite will enterwind layers which have been slowed down by the frictional influence ofthe surface of the earth, producing effects similar to those which maybe accomplished by allowing string to run out.

The alternate version of the invention shown in FIG- URES 12 and 13employs details of construction typically like those of the preferredversion shown in FIGURE 1, except that a single piece lifting surfacereplaces the two piece wing and tail, and, flaps 22 are used rearward ofthe rear portion of the border string loop, to produce any desiredplanform at the wing trailing edge.

The details of the alternate forms of the invention shown in FIGURES 16through 19 will be apparent to anyone who is well versed in the art ofkite construction. These kites have been described earlier in thisapplication.

It is apparent that many other variations of the invention could bedescribed, for example using aerodynamic slots in the jib-likestabilizers and numerous other such refinements, without departing fromthe spirit of this invention. Accordingly, the invention is to belimited in scope only as defined in the appended claims.

I claim:

1. A kite comprising a lifting surface, the forward region of saidlifting surface comprising a jib-like stabilizer surface of generallytriangular form lying in the region immediately forward of a lateralstick member, said lateral stick member sloping rearwardly and outwardlynear its outer tip, said stabilizer surface being supported along itsrearward edge by said lateral stick member, said stabilizer surf-acebeing held spread forwardly by a tension member attached to its outerforward edge, said tension member being attached to the lateralextremity of said lateral stick member and to the forward extremity of alongitudinal stick member, said longitudinal stick member being attachedto said lifting surface and extending forward well clear of saidjib-like surface and well clear of said lifting surface.

2. A kite comprising a lifting surface having a lateral tip at a lateralextremity thereof, said lifting surface having an upwardly concave form,a longitudinal support member of relatively dense material supportingsaid lifting surface and extending forward well clear of said liftingsurface, and a lateral support member supporting said lifting surfacesituated rearward of the leading edge of said lifting surface, saidlateral support member supporting the region of said lateral tip of saidlifting surface, said lateral support member sloping rearwardly andoutwardly near its outer tip.

3. A kite comprising two crossed sticks, a border string in tensionforming a loop around the ends of said sticks, said border string beingattached to said tips and holding said sitcks bent concave upwardly, alifting surface attached to said border string, the forward portion ofthe first of said crossed sticks extending forward well clear of saidlifting surface, the outer tip of the second of said crossed stickssloping rearwardly and outwardly, and the leading edge of said liftingsurface being situated forward of the second of said crossed sticks.

4. A kite comprising frame members including a longitudinal member and alateral member, a string attached to one end of said lateral memberthence directly to the rearward end of said longitudinal member andthence directly to the other end of said lateral member, a laterallyarranged wing surface attached at its lateral ends to said string closeto the ends of said lateral frame member and attached in its centralregion to said longitudinal member, and a trailing edge on said wingsurface lying rearward of said lateral member and lying between saidstring and said longitudinal member, said trailing edge being located atall points well forward of the rearward end of said longitudinal member,leaving an open space of substantial size at the rear of said kitebordered by said trailing edge and by the rearmost portion of saidstring member.

5. In the kite of claim 4, a tail surface member attached to said stringpartially filling said open space.

6. A kite comprising frame members including a longitudinal member and alateral member, said lateral member sloping rearwardly and outwardlynear its outer tip, a string attached to one end of said lateral memberthence to the forward end of said longitudinal member and thence to theother end of said lateral member, a laterally arranged wing surfaceattached at its lateral ends to said string close to the ends of saidlateral frame member and attached in its central region to saidlongitudinal member, and'a leading edge on said wing surface located atall points well rearward of the forward end of said longitudinal member.

7. A kite comprising lifting surface means which includes all liftingsurfaces on the kite, said lifting surface means comprising a liftingsurface having lateral tips at opposite lateral extremities thereof,said lifting surface having an upwardly concave form laterally andlongitudinally; a narrow longitudinal stick member of relatively stickmember of relatively dense material attached longitudinally across saidlifting surface and extending forward well clear of said lifting surfaceand well clear forwardly of the most forward portion of said liftingsurface means; and a lateral stick member of upwardly and rearwardlyconcave form extending laterally across said lifting surface supportingsaid surface and supporting the regions of said lateral tips of saidsurface.

8. A kite comprising lifting surface means which includes all liftingsurfaces on the kite, said lifting surface means comprising a liftingsurface having lateral tips at the laterally outward extremitiesthereof; a narrow member of relatively dense material supporting saidlifting surface and extending forward well clear of said lifting surfaceand well clear forwardly of the most forward portion of said liftingsurface means; said lifting surface having an upwardly concave formlaterally and longitudinally, said lifting surface having locallyincreased concavity of form laterally and longitudinally in the forwardregion of said lateral tips thereof.

9. A kite comprising lifting surface means which includes all liftingsurfaces on the kite, said lifting surface means comprising a liftingsurface; a narrow member of relatively dense material attached to saidkite and extending forward well clear of said lifting surface and wellclear forwardly of the most forward portion of said lifting surfacemeans; and a forwardly-upwardly sloping, rearwardlyoutwardly skewedstabilizer surface attached to said lifting surface adjacent to alateral extremity thereof.

10. In the kite of claim 9, adjustment means attached to said stabilizersurface for adjusting the angle of tilt of said stabilizer surface.

11. A kite comprising lifting surface means which includes all liftingsurfaces on the kite, said lifting surface means comprising a liftingsurface, said lifting surface having a lateral tip at a laterallyoutward extremity thereof; a narrow member of relatively dense materialattached to said lifting surface extending forward well clear of saidlifting surface and well clear forwardly of the most forward portion ofsaid lifting surface means; a leading edge at the forward boundary ofsaid lifting surface, a forward region of said lifting surface adjoiningsaid leading edge, said forward region extending laterally from saidnarrow member to said lateral tip of said lifting surface, said forwardregion of said lifting surface sloping forwardly and upwardly.

12. In the kite of claim 11, the outer portion of said forward region ofsaid lifting surface skewing rearwardly and outwardly.

13. A kite comprising lifting surface means which includes all liftingsurfaces on the kite, a wing stick and a body stick crossed and attachedtogether, a border string in tension forming a loop encompassing saidsticks and attached to the tips thereof, said border string holding saidsticks bowed concave upwardly, said lifting surface means comprising alifting surface, said lifting surface attached to said string loop, saidbody stick extending forward well clear of said lifting surface and wellclear forwardly of the most forward portion of said lifting surfacemeans, and upwardly-forwardly sloping outwardlyrearwardly skewedjib-like stabilizing surfaces adjacent to the lateral tips of saidlifting surface.

14. In the kite of claim 13, the midpoint of said wing stick beingattached to said body stick at a point relatively more forward than thepoints of attachment of the tips of said wing sick to said borderstring, the described attachment of said wing stick holding it concaverearwardly.

(References on following page) 13 14 References Cited 3,074,672 1/196 3-Hanrahan 244--153 UNITED STATES PATENTS 3,116,90 1/1964 Gould A 4 5/1924Wanner 244153 FOREIGN TENTS 1927 Dahl 244 153 5 212,887 2/1958Australla.

g; Gurwick 156-179 X MILTON BUCHL-ER, Primary Examiner.

9 WOlfi 244-153 6/1940 Irvin FERGUS S. MIDDLETON, Exa mmer. 4/ 1960Riker 244153 P. E. SAUB'ERER, Assistant Examiner.

1. A KITE COMPRISING A LIFTING SURFACE, THE FORWARD REGION OF SAIDLIFTING SURFACE COMPRISING A JIB-LIKE STABILIZER SURFACE OF GENERALLYTRIANGULAR FORM LYING IN THE REGION IMMEDIATELY FORWARD OF A LATERALSTICK MEMBER, SAID LATERAL STICK MEMBER SLOPING REARWARDLY AND OUTWARDLYNEAR ITS OUTER TIP, SAID STABILIZER SURFACE BEING SUPPORTED ALONG ITSREARWARD EDGE BY SAID LATERAL STICK MEMBER, SAID STABILIZER SURFACEBEING HELD SPREAD FORWARDLY BY A TENSION MEMBER ATTACHED TO ITS OUTERFORWARD EDGE, SAID TENSION MEMBER BEING ATTACHED TO THE LATERALEXTREMITY OF SAID LATERAL STICK MEMBER AND TO THE FORWARD EXTREMITY OF ALONGITUDINAL STICK MEMBER, SAID LONGITUDINAL STICK MEMBER BEING ATTACHEDTO SAID LIFTING SURFACE AND EXTENDING FORWARD WELL CLEAR OF SAIDJIB-LIKE SURFACE AND WELL CLEAR OF SAID LIFTING SURFACE.